Multi-organ failure (MOF) remains a major unresolved medical problem. MOF develops in the most severely ill patients who have sepsis, particularly when the latter develops after major surgery or trauma. It occurs also with greater frequency and severity in elderly patients, those with diabetes mellitus, underlying cardiovascular disease and impaired immune defenses. MOF is characterized by shock, acute renal failure (ARF), leaky cell membranes, dysfunction of lungs, liver, heart, blood vessels and other organs. Mortality due to MOF approaches 100% despite the utilization of the most aggressive forms of therapy, including intubation and ventilatory support, administration of vasopressors and antibiotics, steroids, hemodialysis and parenteral nutrition. Many of these patients have serious impairment of the healing of surgical or trauma wound, and, when infected, these wounds further contribute to recurrent infections, morbidity and death.
ARF is defined as an acute deterioration in renal excretory function within hours or days, resulting in the accumulation of “uremic toxins,” and, importantly, a rise in the blood levels of potassium, hydrogen and other ions, all of which contribute to life threatening multisystem complications such as bleeding, seizures, cardiac arrhythmias or arrest, and possible volume overload with pulmonary congestion and poor oxygen uptake. The most common cause of ARF is an ischemic insult of the kidney resulting in injury of renal tubular and postglomerular vascular endothelial cells. The principal etiologies for this ischemic form of ARF include intravascular volume contraction, resulting from bleeding, thrombotic events, shock, sepsis, major cardiovascular surgery, arterial stenoses, and others. Nephrotoxic forms of ARF can be caused by radiocontrast agents, significant numbers of frequently used medications such as chemotherapeutic drugs, antibiotics and certain immunosuppressants such as cyclosporine. Patients most at risk for all forms of ARF include diabetics, those with underlying kidney, liver, cardiovascular disease, the elderly, recipients of a bone marrow transplant, and those with cancer or other debilitating disorders.
Both ischemic and nephrotoxic forms of ARF result in dysfunction and death of renal tubular and microvascular endothelial cells. Sublethally injured tubular cells dedifferentiate, lose their polarity and express vimentin, a mesenchymal cell marker, and Pax-2, a transcription factor that is normally only expressed in the process of mesenchymal-epithelial transdifferentiation in the embryonic kidney. Injured endothelial cells also exhibit characteristic changes.
The kidney, even after severe acute insults, has the remarkable capacity of self-regeneration and consequent re-establishment of nearly normal function. It is thought that the regeneration of injured nephron segments is the result of migration, proliferation and redifferentation of surviving tubular and endothelial cells. However, the self-regeneration capacity of the surviving tubular and vascular endothelial cells may be exceeded in severe ARF. Patients with isolated ARF from any cause, i.e., ARF that occurs without MOF, continue to have a mortality in excess of 50%. This dismal prognosis has not improved despite intensive care support, hemodialysis, and the recent use of atrial natriuretic peptide, Insulin-like Growth Factor-I (IGF-I), more biocompatible dialysis membranes, continuous hemodialysis, and other interventions. An urgent need exists to enhance the kidney's self-defense and autoregenerative capacity after severe injury.
Another acute form of renal failure, transplant-associated acute renal failure (TA-ARF), also termed early graft dysfunction (EGD), commonly develops upon kidney transplantation, mainly in patients receiving transplants from cadaveric donors, although TA-ARF may also occur in patients receiving a living related donor kidney. Up to 50% of currently performed kidney transplants utilize cadaveric donors. Kidney recipients who develop significant TA-ARF require treatment with hemodialysis until graft function recovers. The risk of TA-ARF is increased with elderly donors and recipients, marginal graft quality, significant comorbidities and prior transplants in the recipient, and an extended period of time between harvest of the donor kidney from a cadaveric donor and its implantation into the recipient, known as “cold ischemia time.” Early graft dysfunction or TA-ARF has serious long-term consequences, including accelerated graft loss due to progressive, irreversible loss in kidney function that is initiated by TA-ARF, and an increased incidence of acute rejection episodes leading to premature loss of the kidney graft. Therefore, a great need exists to provide a treatment for early graft dysfunction due to TA-ARF or EGD.
Chronic renal failure (CRF) or Chronic Kidney Disease (CKD) is the progressive loss of nephrons and consequent loss of renal function, resulting in End Stage Renal Disease (ESRD), at which time patient survival depends on dialysis support or kidney transplantation. The progressive loss of nephrons, i.e., glomeruli, tubuli and microvasculature, appears to result from self-perpetuating fibrotic, inflammatory and sclerosing processes, most prominently manifested in the glomeruli and renal interstitium. The loss of nephrons is most commonly initiated by diabetic nephropathy, glomerulonephritides, many proteinuric disorders, hypertension, vasculitic, inflammatory and other injuries to the kidney. Currently available forms of therapy, such as the administration of angiotensin converting enzyme inhibitors, angiotensin receptor blockers, other anti-hypertensive and anti-inflammatory drugs such as steroids, cyclosporine and others, lipid lowering agents, omega-3 fatty acids, a low protein diet, and optimal weight, blood pressure and blood sugar control, particularly in diabetics, can significantly slow and occasionally arrest the chronic loss of kidney function in the above conditions. The development of ESRD can be prevented in some compliant patients and delayed others. Despite these successes, the annual growth of patient numbers with ESRD, requiring chronic dialysis or transplantation, remains at 6%, representing a continuously growing medical and financial burden. There exists an urgent need for the development of new interventions for the effective treatment of CRF or CKD and thereby ESRD, to treat patients who fail to respond to conventional therapy, i.e., whose renal function continues to deteriorate. Stem cell treatment will be provided to arrest/reverse the fibrotic processes in the kidney.
Taken together, therapies that are currently utilized in the treatment of ARF, the treatment of established ARF of native kidneys per se or as part of MOF, and ARF of the transplanted kidney, and organ failure in general have not succeeded to significantly improve morbidity and mortality in this large group of patients. Consequently, there exists an urgent need for the improved treatment of MOF, renal dysfunction, and organ failure.
Very promising pre-clinical studies in animals and a few early phase clinical trials administer bone marrow-derived hematopoietic stem cells for the repair or protection of one specific organ such as the heart, small blood vessels, brain, spinal cord, liver and others. These treatments have generally used only a single population of bone-marrow stem cells, either Hematopoietic (HSC) or Mesenchymal Stem Cells (MSC), and obtained results are very encouraging in experimental stroke, spinal cord injury, and myocardial infarction. The intracoronary administration of stem cells in humans with myocardial infarction or coronary artery disease has most recently been reported to result in significant adverse events such as acute myocardial infarction, other complications and death. Peripheral administration of stem cells or the direct injection into the injured myocardium showed more favorable results both in animal and Phase I trials. MSC have been infused into patients a few weeks after they first received a bone marrow transplant in the treatment of cancers, leukemias, osteogenesis imperfecta, and Hurler's syndrome to accelerate reconstitution of adequate hematopoiesis. Effective treatment of osteogenesis imperfecta and Hurler's syndrome has been shown using MSC. Importantly, administration of a mixture of HSC and MSC, known to physiologically cooperate in the maintenance of hematopoiesis in the bone marrow, has, until now (see below) not been utilized for the treatment of any of the above listed renal disorders, MOF or wound healing.
In ARF (native kidneys, transplanted kidney), microvascular endothelial cells and proximal as well as distal tubular cells become dysfunctional and are destroyed when injured, insults that together mediate the acute loss of kidney function. Successful recovery from ARF depends directly on the repair of injured renal microvessels and tubular segments. Since both HSC and MSC possess a remarkable level of plasticity, i.e., are capable to differentiate into several non-hematopoietic cell types (neurons, heart, muscle, liver, vascular and other cells) including renal tubular and vascular endothelial cells, pre-clinical studies were begun to test the concept that the co-administration of HSC and MSC may be more renoprotective than the administration of either HSC or MSC alone, as it reproduces their mutually supportive capacity in the bone marrow. Studies demonstrated that MSC can be induced, using co-culture, conditioned media and injury models, to differentiate in vitro both into vascular endothelial and tubular cell phenotypes. In addition, syngeneic vascular endothelial cells (EC) or EC derived from MSC were tested to determine whether EC could function in rats with ARF as kidney protective renal EC precursors. Without wishing to be bound to any particular theory, the present inventor believes that microvascular dysfunction and EC injury and death are prominent mediators of inadequate renal blood flow in ARF, and that the delivery of “healthy” EC or their precursors could improve renal hemodynamics, thereby augmenting tubular cell survival, protecting renal function and hastening tissue repair. The results of these studies to date show: (1) all types of EC or EC precursors, derived from all tested sources, significantly protect renal function and improve outcome in rats with established ischemic ARF, reducing mortality from ˜40% to <5%; (2) MSC administration alone results in delayed but significantly accelerated recovery of renal function; (3) HSC infusion alone shows similar or slightly less improvement in functional recovery compared to that obtained with MSC; (4) the administration of a defined mix of HSC and MSC, as discussed below, appears highly effective in the treatment of ARF, the rapid reestablishment of adequate renal function after ARF, and essential elimination of animal mortality.
In the kidney, the administration of pluripotent stem cells, derived from hematopoietic or non-hematopoietic sources, can be utilized for repair of critically damaged kidney tissues. The physical or functional loss of reno-vascular endothelial and tubular cells and thus renal function, whether occurring in acute or chronic renal failure, is a serious medical condition that will be ameliorated by the present invention. Any slowing, arrest, or reversal of the decline in renal function provided by the present invention will be enormously beneficial to the affected patients with ARF, TA-ARF, CRF, or any kidney failure-associated systemic dysfunction, MOF or wound healing.